Standard molding base



Dec. 6, 1949 T. QuARNs-rRoM 2,490,229

STANDARD MOLDING' BASE Filed March 2l, 1946 @www ,p-W.

Patented Dec. 6, 1949 2,490,229 STANDARD MODDING BASE Ivar T. Quarnstrom, New Haven, Mich. Y Application March 21, 1946, serial No. 656,037'

2 Claims. l

This invention relates to a mold base for plastic injection molding, and more particularly to an ejector pl-ate construction employed in said mold l base.

Heretofore in mold bases of this type considerable diiculty has been encountered due to binding of the mold ejector pins relative to the openings within the mold base through which said pins are adapted to slidably pass. Unless the ejector plate is in perfect parallelism at all times, the ejector pins carried thereby will have the tendency to bind,

It is therefore the object of this invention to provide means for positively maintaining the ejector plate at all times parallel to the horivzontal surfaces of the mold members, whereby the ejector pins will slide freely through the ejector pin openings.

It is the further object of this invention to provide a plurality of novel push-back or return pins for the ejector plate, wherein said pins also extend through the ejector plate with their ends sli-dably positioned through corresponding openings in the mold base.

These and other objects will be seen from the following specifications in conjunction with the attendant drawing of which;

Figure 1 is a plan view of the mold base; and

Figure 2 is an elevational section thereof on line 2-2 of Figure 1.

It will be understood that the above drawing illustrates merely a preferable embodiment of the invention, vand that other embodiments are contemplated Within the scope of the claims hereafter set out.

The standard mold base consists of a rectangular anchor plate I I with the two upright parallel members I2 and I3 carried therein in spaced relation. Ledge portions I4 and I5 extend beyond upright members I2 and I3 providing a means of attachment of anchor plate Ii to the movable member of a molding machine.

Rectangularr'ear cavity retainer plate I 6 is p0- sitioned and supported upon the top edges of parallel members I2 and I 3, said retainer plate being removable'v and interchangeable. A corresponding frontzlcavity retainer plate I'I is provided similar in'shape to said rear cavity plate for compressivefcooperative engagement with respect thereto during the molding operation.

The upper surface of plate I6 and the lower surface of plate I 'I are initially blank, but are adapted to have impressed or cut therein, or inserted within openings therein, corresponding and mating cores and cavities within which is injected a plastic material to be molded.

Another anchor plate I8 corresponding to anchor plate I I is suitably secured to front cavity plate I'I and similarly the edges I9 and 20 of plate I8 extend beyond the edges.v of plate I1 to permit clamping thereof within `the stationary portion of a molding machine.

A rectangular ejector plate is indicated yat 2| longitudinally disposed between the two parallel members I2 and I3 in spaced relation, adapted for manually or ymechanically actuated upward movement therebetween. A secondary ejector' plate 22 secured uponejector plate 2I is adapted to retain and secure pushback pins 23 in upright position at right angles to the horizontal surfaces of ejector plate 2 I.

The four push-back pins 23 shown herein each have a `central annular flange 24 which rests upon ejector plate 2| and nts within a corresponding opening insecondary ejector plate 22, whereby with plate Z2 suitably secured to plate 2l said pins 23 are immovably retained.

Said pins project through ejector plate2I--22 from both sides thereof with one end slidably extended through a corresponding opening in plate I6. The other end projects' from the opposite side of ejector plate 2I-22 and is slidably posis tioned within corresponding co-axial openings 25 :but also act as a positiva-stop for the ejector plate in its returned inoperative position, in

sljlnaced relation to the top surface of anchor plate The end portions 29 of push-pins 23 are engaged by the bottom surface of cavity plate I1 as cavity plates I6 and Ilare brought together within a molding machine for the molding operation.

Ejector pins 30 are shown in Fig. 2 secured to ejector plate 2I22 with their ends extending therefrom and adapted to extend through corresponding openings in` plate I6 and core 32 therein. The latter is positioned by the ymold maker Within cavity plate I6 in corresponding and cooperating aligned relation to the cavity member 33 which is similarly Positioned Within retainer plate Il.

Vis at all times guided by return pins 23'.

After a molding operation plate I6 and anchor plate II are withdrawn by operation of a molding machine. Ejector plate 2I-22 is withdrawn only partially and then stopped from further movement by engagement with stationary base 34 which extends from the molding machine and loosely through opening 35 in anchor plate I I.

Thus it is seen that the ends of pins 39 as Well as the ends 29 of return pins 23 will project above the top surface of plate I6 as the same is further withdrawn by the molding machine. In this manner the molded element 36 is ejected from core 32 by the action of pins 30.

By operation of the molding machine, and inv anticipation of the next molding operation, plates I I and I6 are projected towards stationary front cavity plate I1 so that initially the push-back pins 23 are operatively engaged by the surface of plate I1. Further movement of plate I6 up to engagement with plate I1 eiects the complete .return of push-back pins 23 and ejector'plate 2I--22 to their initial inoperative position as illustrated in Fig. 2.

Reciprocal movementoff ejector plate 2I-22 29 thereof are adapted for sliding movement within corresponding openings in plate IB, while their opposite ends are adapted for sliding movement within the spaced coaxially alignedbushings 26 in anchor plate II. 'Thus it is guaranteed their guide openings eliminating any possible binding. While the lpresent drawing illustrates merely one core and cavity positioned respectively within cavity retainer plates I6 and I1, it

will be understood that normally there may be a.

.plurality of such cores and cavities. Consequently there will be an increased number of ejector pins corresponding to each core and cavity so that it .is doubly important to prevent binding action of the ejector pins relative tof their .guide openings formed within plate I'E and' the cores carried thereby.

It will be noted that the lower ends 28 of push-back pins 23 will be in engagement with bushings 26 throughout the greater portion of the upward movement relatively of ejector plate 2 I-22. In the event that -a greater movement is contemplated it will be seen that said ejector plate will be adequately guided by the approximate full length of the upper portion 29 lof pushback pins 23 extending through the corresponding openings in cavity retainer plate IB.

Having described my invention reference should now be had to the claims which follow yfor Vdetermining .the scope thereof.

Ends i other ends slidably extending within corresponding coaxial openings in said rear retainer plate, said other ends being operatively engageable f with said front cavity retainer plate as said retainer plates are brought together on closure of the mold.

2. In a mold for injection plastic molding, a

,movable anchor plate, a rear cavity retainer ,plate carried thereby in spaced relation thereto,

a stationary anchor plate, a front cavity yre*- tainer plate carried thereby, a reciprocal ejector plate intermediate the movable anchor plate and rear retainer plate, a plurality of annularly anged bushings positioned Within openings in said movable anchor plate, and a plurality of return pins secured to and extending through said ejector plate with one of their ends slidably extending within said bushings, and with their other ends slidably extending within corresponding coaxial openings in said rear retainer plate, the flanged portions of said bushings projecting above said movable anchor plate acting as stops for said ejector plate to maintain a spaced relation between said ejector plate and movable anchor plate in its inoperative position, said other ends being operatively engageable with said front cavity retainer plate as said retainer plates are brought together on closure of the mold.

IVAR T. QUARNSTROM.

REFERENCES CITED The following references are of recordin the le of this patent:

UNITED STATES PATENTS Milano Jan. 25, 1944 OTHER REFERENCES Modern Plastics, May 1941, pages 77 and 102. Tool and Die Journal, pages 84-89, Jan. 1943. British Plastics, pages 10G-114, July 1943. 

